Zone venting in a fluid cartridge

ABSTRACT

In one embodiment, a cartridge includes: a housing having a chamber therein for holding a fluid; a vent at a first part of the chamber; a porous fluid holding material in the chamber; an outlet from the chamber; and a hole extending through the fluid holding material from the first part of the chamber to a second part of the chamber at a location away from the outlet such that the second part of the chamber is vented through the hole but the outlet is not vented through the hole.

BACKGROUND

In some inkjet printer ink cartridges the ink is held inside thecartridge in a foam ink holding material. Although the foam usuallyoccupies substantially all of an ink holding chamber inside thecartridge, small voids or pockets around the foam may exist,particularly along the bottom and in corners of the ink holding chamber.Also, it may be desirable in some cartridges to only partially fill anink holding chamber with foam, for example to vary the amount of inkheld in the cartridge without also changing the size or shape of the inkholding chamber, thus leaving areas of the ink holding chamberunoccupied by foam. A foam filled ink holding chamber is usually ventedto the atmosphere through the lid of the cartridge. Air may becometrapped in voids or pockets around the foam or in other areas of the inkholding chamber not occupied by foam if those areas are sealed off fromthe lid vents. Improper venting in these areas may inhibit the abilityof the foam to absorb (or re-absorb) ink that may collect in these areasor otherwise adversely affect performance of the cartridge.

DRAWINGS

FIG. 1 is a perspective view illustrating the exterior of a black orother single-color ink cartridge.

FIG. 2 is a top plan view of the ink cartridge of FIG. 1.

FIGS. 3 and 4 are elevation section views of the cartridge of FIG. 1taken along the lines 3-3 and 4-4, respectively, in FIG. 2 illustratingone embodiment of the disclosure.

FIG. 5 is a plan section view of the ink cartridge of FIG. 1 taken alongthe line 5-5 in FIG. 3.

FIG. 6 is a detail section view taken from FIG. 5 showing a portion ofthe printhead in the cartridge of FIG. 1.

FIGS. 7 and 8 are elevation and plan section views, respectively, of anink cartridge such as the ink cartridge shown in FIGS. 1 and 2illustrating another embodiment of the disclosure.

FIGS. 9 and 10 are plan section views an ink cartridge such as the inkcartridge shown in FIGS. 1 and 2 illustrating another embodiment of thedisclosure.

FIG. 11 is a perspective view illustrating the exterior of a three-colorink cartridge.

FIG. 12 is a top plan view of the ink cartridge of FIG. 11.

FIG. 13 is a plan section view of the ink cartridge of FIG. 11 takenalong the line 13-13 in FIG. 14 illustrating another embodiment of thedisclosure.

FIG. 14 is an elevation section view of the cartridge of FIG. 11 takenalong the line 14-14 in FIG. 15.

FIGS. 15 and 16 are elevation section views of the ink cartridge of FIG.11 taken along the lines 15-15 and 16-16, respectively, in FIG. 14.

FIG. 17 is a detail section view taken from FIG. 16 showing a portion ofthe printhead in the cartridge of FIG. 11.

DETAILED DESCRIPTION

Embodiments of the disclosure were developed in an effort to selectivelyvent free ink regions in an ink cartridge—regions not occupied by thefoam or other ink holding material. FIGS. 1-15 illustrate single-colorand tri-color ink cartridges for a thermal inkjet printer. Embodimentsof the invention might also be implemented with respect to an inkcartridge for other types of inkjet printers, a piezoelectric typeinkjet printer for example, or in other kinds of fluid cartridges.

“Vent” or “venting” as used in this document means exposing something toatmospheric pressure. A “vent” as used in this document, therefore, is astructure or feature through which something is exposed to atmosphericpressure.

FIG. 1 is a perspective view of a single-color (typically black) inkcartridge 10. FIG. 2 is a top plan view and FIGS. 3-5 are section views,respectively, of ink cartridge 10. The ink holding foam is cut-away inFIG. 5 to more clearly illustrate some of the internal features of inkcartridge 10. FIG. 6 is a detail section view of a portion of theprinthead in cartridge 10.

Referring to FIGS. 1-6, cartridge 10 includes a printhead 12 located atthe bottom of cartridge 10 below an ink holding chamber 14. Printhead 12includes a nozzle plate 16 with two arrays 18, 20 of ink ejectionnozzles 22. In the embodiment shown, each array 18, 20 is a single rowof nozzles 22. As shown in the detail view of FIG. 6, firing resistors24 formed on an integrated circuit chip 26 are positioned behind inkejection nozzles 22. A flexible circuit 28 carries electrical tracesfrom external contact pads 30 to firing resistors 24. When ink cartridge10 is installed in a printer, cartridge 10 is electrically connected tothe printer controller through contact pads 30. In operation, theprinter controller selectively energizes firing resistors 24 through thesignal traces in flexible circuit 28. When a firing resistor 24 isenergized, ink in a vaporization chamber 32 next to a resistor 24 isvaporized, ejecting a droplet of ink through a nozzle 22 on to the printmedia. The low pressure created by ejection of the ink droplet andcooling of chamber 32 then draws in ink to refill vaporization chamber32 in preparation for the next ejection. The flow of ink throughprinthead 12 is illustrated by arrows 34 in FIG. 6.

Ink is held in foam 36 or another suitable porous material in inkchamber 14 formed within a cartridge housing 38. Housing 38, which istypically molded plastic, may be molded as a single unit, molded as twoparts (e.g., a lid 40 and a body 42) or constructed of any number ofseparate parts fastened to one another in the desired configuration. Anoutlet 44 to printhead 12 is located near the bottom of ink chamber 14.A filter 46 covering outlet 44 is often used to keep contaminants, airbubbles and ink flow surges from entering printhead 12 during operation.Foam 36 is usually compressed around filter 46 and outlet 44 to increaseits capillarity in the region of outlet 44. As ink is depleted from foam36, the increased capillarity near outlet 44 tends to draw ink from allother portions of foam 36 to maximize the amount of ink drawn fromchamber 14.

Referring now specifically to FIGS. 2-4, openings 48 formed in lid 40are covered by a label or other suitable adhesive sheet 50. Openings 48are exposed to the atmosphere through circuitous tunnels 52. Each tunnel52, commonly referred to as a labyrinth, is formed by a recess in thetop of lid 40 that extends past the edge of label 50. Labyrinths, whichare well known in the art of inkjet printing, are commonly used forventing ink cartridges to slow the rate of evaporation. Spacers 54projecting down from the bottom of lid 40 hold foam 36 off lid 40 toprovide a gap 56 between foam 36 and lid 40. Gap 56 helps vent inkholding chamber 14 to the atmosphere through openings 48 and labyrinths52.

Gap 56 also helps prevent ink wicking out from foam 36 through the holes48 and blocking the labyrinths 52. If labyrinths 52 become blocked, thebackpressure (i.e., negative pressure) in foam 36 may become unstable.Backpressure in foam 36 is generated by the capillary forces created bymenisci at the interfaces in foam 36 between ink and air. Venting gap 36through openings 48 and labyrinths 52 maintains the pressure in gap 56at atmospheric pressure. Changes in pressure in gap 56 changes thebackpressure in foam 36. If the pressure in gap 56 is higher thanatmospheric pressure (i.e., positive pressure), the backpressure in foam36 becomes less negative, the force holding ink in cartridge 10 is lessthan normal and ink may drool from nozzles 22. If the pressure in gap 56is less than atmospheric pressure, the backpressure in foam 36 becomesmore negative, the force holding ink in cartridge 10 is greater thannormal and ink will flow less quickly (or not at all) to printhead 12during printing.

Referring to FIGS. 3-5, holes 58 are formed through foam 36 to ventselected areas or “zones” of ink chamber 14. In the exampleconfiguration shown in FIGS. 3-5, a pair of two holes 58 vent a void 60under foam 36 around outlet 44. Void 60 is an area around outlet 44 notoccupied by foam 36. Without vent holes 58 in foam 36, void 60 may besealed off from lid vents 48 and, consequently, any free ink (ink notheld in foam 36) collecting in void 60 may not be absorbed orre-absorbed into foam 36.

Other configurations are possible. For example, in the configuration ofcartridge 10 shown in FIGS. 7 and 8, ink chamber 14 includes a free inkzone 62 at a rear part of chamber 14 defined by a partition 64separating free ink zone 62 from outlet 44. Foam 36 includes two foamblocks 66 and 68. Free ink zone 62 is vented through holes 70 in upper,cap foam block 68. Lower, filter cap foam block 66 covering outlet 44and filter 46 is constrained by partition 64 and chamber walls 72. Thus,block 66 may be compressed around filter 46 and outlet 44 to increasethe capillarity in the region of outlet 44. As ink is depleted fromblock 66, the increased capillarity near outlet 44 draws in ink fromother portions of block 66 and from block 68. This capillary action alsodraws ink 74 from free ink in zone 62 up along partition 64 and chamberwalls 72 into block 68. Absent the consistent venting provided by holes70, free ink zone 62 may or may not be vented depending on the level ofink in foam 68, resulting in the partial and/or unintentional venting ofzone 62. Thus, consistent venting through holes 70 improves control over“drool” caused by erratic changes in backpressure in foam 38 and overthe absorption of free ink 74 into foam 68.

In other examples, vent holes are used selectively to vent one or moremultiple free ink zones. FIGS. 9-10 illustrate different ventingconfigurations for an ink cartridge 10 partitioned into multiple freeink zones 62 a-62 d below foam block 68. In the configuration shown inFIG. 9, each free ink zone 62 a-62 d is vented through a correspondinghole 70 a-70 d so that any free ink in zones 62 a-62 d tends to beconstantly drawn up into foam 68. In the configuration of FIG. 10, onlythe rear zones 62 c and 62 d are vented through associated vent holes 70c and 70 d. In the configuration of FIG. 10, any ink in zones 62 c and62 d tends constantly to be drawn up into foam 68. The absorption of anyink in zones 62 a and 62 b will be controlled primarily by the conditionof foam 68. Thus, when the level of ink in foam 68 is such that zones 62a and 62 b are effectively sealed off from gap 56 and lid vents 48, thenink in zones 62 a and 62 b will tend not to be drawn up into foam 68,remaining largely unabsorbed by foam 68. When the level of ink in foam68 is such that zones 62 a and 62 b are effectively exposed to gap 56and lid vents 48, venting zones 62 a and 62 b (for example as foam 68dries out in the area above zones 62 a and 62 b), then ink in zones 62 aand 62 b will tend to be drawn up into foam 68 until foam 68 issufficiently saturated with ink to again seal off zones 62 a and 62 bfrom gap 56 and lid vents 48.

The configuration of FIG. 9 corresponds to an ink fill scenario forcartridge 10 in which the volume of ink inserted into chamber 14 is notgreater than the holding capacity of foam 36 and 38. In this ink fillscenario, free ink zones 62 a-62 d are not used purposely to store ink.The configuration of FIG. 10 corresponds to an ink fill scenario forcartridge 10 in which free ink zones 62 a and 62 b may be used purposelyto store ink. In this ink fill scenario, ink inserted into zones 62 aand 62 b will tend to remain there until ink is depleted from foam 36,allowing venting of zones 62 a, 62 b through foam 36 as described above.The use of different configurations for selectively venting free inkzones 62 within ink holding chamber 14 thus allows for a correspondingvariety of ink fill levels in a single configuration of cartridgehousing 38.

FIGS. 11-17 illustrate a three color ink cartridge 80 for a thermalinkjet printer. FIG. 11 is a perspective view of cartridge 80. FIG. 12is a top plan view and FIGS. 13-16 are section views of ink cartridge80. The ink holding foam is cut-away in FIG. 13 to more clearlyillustrate some of the internal features of ink cartridge 80. FIG. 17 isa detail section view of a portion of the printhead in cartridge 80.Referring to FIGS. 13-17, cartridge 80 includes a printhead 82 locatedat the bottom of cartridge 80 below ink chambers 84, 86 and 88.Printhead 82 includes a nozzle plate 90 with three arrays 92, 94 and 96of ink ejection nozzles 98. In the embodiment shown, each array 92, 94and 96 is a single row of nozzles 98. As shown in FIG. 15, firingresistors 100 formed on an integrated circuit chip 102 are positionedbehind ink ejection nozzles 98. A flexible circuit 104 carrieselectrical traces from external contact pads 106 to firing resistors100.

When ink cartridge 80 is installed in a printer, cartridge 80 iselectrically connected to the printer controller through contact pads106. In operation, the printer controller selectively energizes firingresistors 100 through the signal traces in flexible circuit 104. When afiring resistor 100 is energized, ink in a vaporization chamber 108(FIG. 17) next to a resistor 100 is vaporized, ejecting a droplet of inkthrough nozzle 98 on to the print media. The low pressure created byejection of the ink droplet and cooling of chamber 108 then draws in inkto refill vaporization chamber 88 in preparation for the next ejection.The flow of ink through printhead 102 is illustrated by arrows 110 inFIG. 17.

Referring now to the section views of FIGS. 13-16, ink is stored inthree chambers 84, 86 and 88 formed within cartridge housing 112. Eachchamber 84, 86 and 88 may be used to store a different color ink, cyan,magenta and yellow for example. Ink chambers 84, 86 and 88 are separatedfrom one another by partitions 114 and 116. Housing 112, which istypically formed from a plastic material, may be molded as a singleunit, molded as two parts (e.g., a lid 118 and a body 120 that includespartitions 114 and 116) or constructed of any number of separate partsfastened to one another in the desired configuration. An outlet 122, 124and 126 is located near the bottom of each ink chamber 84, 86 and 88,respectively. A conduit 128, 130 and 132 leads from each outlet 122, 124and 126, respectively. Ink passes from each chamber 84, 86 or 88 througha corresponding outlet 122, 124 or 126 and conduit 128, 130 or 132 toprinthead 82, where it is ejected through the corresponding nozzle array92, 94 or 96, as described above.

Ink is held in foam 134 or another suitable porous material in each inkchamber 84, 86 and 88. A filter 136 covering each outlet 122, 124, and126 is typically used to keep contaminants, air bubbles and ink flowsurges from entering printhead 82 during operation. Foam 134 is usuallycompressed around filters 136 and outlets 122, 124 and 126 to increaseits capillarity in the region of outlets 122, 124 and 126. As ink isdepleted from foam 134, the increased capillarity near the outlet tendsto draw ink from all other portions of foam 134 to maximize the amountof ink drawn from each chamber 84, 86 and 88.

Openings 138, 140, and 142 formed in lid 118 are covered by a label orother suitable adhesive sheet 144. Vent openings 138, 140 and 142 areexposed to the atmosphere through circuitous tunnels 146. Each tunnel146, commonly referred to as a labyrinth, is formed by a recess in thetop of lid 118 that extends past the edge of label 144. Spacers 148projecting down from the bottom of lid 118 hold foam 134 off lid 118 toprovide a gap 150 between foam 134 and lid 118. Gap 150 helps vent inkholding chambers 84, 86 and 88 to the atmosphere through openings 138,140, 142 and labyrinths 146. Referring to FIGS. 13-16, holes 152, 154and 156 are formed through foam 134 to vent selected areas or “zones” ofeach ink chamber 84, 86 and 88. In the example configuration shown inFIGS. 13-16, a pair of holes 152 vent a void 158 around outlet 122 inchamber 84. Single holes 154, 156 vent voids 160, 162 in chambers 86,88, respectively.

For effective venting air must be able to pass through each vent hole.Thus, the diameter of each vent hole (or other cross-sectional dimensionfor non-circular holes) should be significantly greater than the nominalpore size of the foam to prevent an ink meniscus clogging the vent hole.Nominal pore sizes in foam ink holding materials commonly used in inkjetink cartridges range from about 0.1 mm for felted foam to about 0.6 mmfor unfelted foam. (Felting refers to the desired and controlledcompression of the pores in the foam.) The cross-sectional dimension ofeach vent hole should be in the range of 5 to 50 times greater than thenominal pore size for these types of foam to help minimize the risk ofmenisci clogging the vent hole. Also, since air transported to thefilter/outlet can seriously degrade performance of the ink cartridge,the vent holes should be located sufficiently far away from the inkfilter(s)/outlet(s) to so that a liquid barrier can form around thefilter/outlet to help prevent venting air to the filter/outlet.

It is advantageous to form the vent holes after the ink holding foam isinserted into the cartridge. Forming vent holes after foam insertion (1)eliminates the risk that the holes will collapse as the foam iscompressed during insertion and (2) helps ensure that vent holeformation does not affect felting in other areas of the foam. In onesuitable technique for forming vent holes, a heated rod having thedesired size and shape is pressed down through the foam after the foamhas been inserted into the ink cartridge. Multiple vent holes may beformed by repeatedly pressing a single rod into the foam at the desiredvent hole locations. Alternatively, an array of heated rods may be usedto form multiple vent holes simultaneously. Unlike water jets, airknives, and other cutting tools that can generate cutting debris, aheated rod reduces the risk of introducing small foam particles into theink holding chamber—particles that could clog the filter or otherwisedegrade performance of the ink cartridge.

The use of a heated rod is also advantageous to control thecharacteristics of the inside surface of the vent hole. At lowertemperatures, about 260° C. for polyurethane foam for example, in whichmore pressure is needed to form the vent hole, the capillary network issoftened by the heat and then mechanically broken and deformed butremains an open network. At higher temperatures, over 300° C. forpolyurethane foam for example, the foam is melted back and the surfacenetwork in the hole is partially or fully closed. The heat affectedzone, however, is minimal and the capillary network beyond this internalshell remains unchanged. There is potential utility in both kinds ofhole structure. The first structure, in which the capillary network isstill open, allows more evaporation from the ink off the larger surfacearea while the second structure, in which the capillary network isclosed, retards evaporation. Also, the number of capillaries availableto affect backpressure in the foam may be controlled in part by thenumber of vent holes and the surface characteristics of the vent holes(open capillary/cell, partially closed capillary/cell, and/or fullyclosed capillary/cell) formed in the ink holding foam. Although theactual temperature used to form a vent hole may vary depending on thespecific type of foam and the desired hole characteristics, it isexpected that a temperature in the range of 225° C. to 400° C. willprovide suitable results for most polyurethane foam ink holdingmaterials.

The article “a” as used in the following claims means one or more. Thus,for example, “a hole extending through the ink holding material” meansone or more holes extending through the ink holding material and,accordingly, a subsequent reference to “the hole” refers the one or moreholes.

The present disclosure has been shown and described with reference tothe foregoing exemplary embodiments. It is to be understood, however,that other forms, details and embodiments may be made without departingfrom the spirit and scope of the disclosure which is defined in thefollowing claims. For example, a cartridge according to otherembodiments may be used to dispense fluids other than inks.

1. A cartridge, comprising: a housing having a chamber therein forholding a fluid; a vent at a first part of the chamber; a porous fluidholding material in the chamber; an outlet from the chamber; and a holeextending through the fluid holding material from the first part of thechamber to a second part of the chamber at a location away from theoutlet such that the second part of the chamber is vented through thehole but the outlet is not vented through the hole.
 2. The cartridge ofclaim 1, wherein the fluid comprises ink.
 3. The cartridge of claim 1,wherein the fluid holding material comprises foam.
 4. The cartridge ofclaim 3, wherein the hole is defined by a surface within the foam, thesurface being characterized a capillary network in the foam.
 5. Thecartridge of claim 3, wherein the hole is defined by a surface withinthe foam, the surface being characterized by a shell in which the foamhas been melted and a capillary network in the foam destroyed, and theshell surrounded by foam in which the capillary network remains intact.6. The cartridge of claim 1, further comprising a printhead affixed tothe housing, the printhead operatively connected to the chamber throughthe outlet.
 7. The cartridge of claim 1, wherein the hole comprises ahole having a cross sectional dimension in the range of 5 to 50 timesgreater than a nominal pore size of the fluid holding material.
 8. Thecartridge of claim 1, wherein: the first part of the chamber comprises atop part of the chamber; the second part of the chamber comprises abottom part of the chamber; and the hole comprises a hole extendingthrough the fluid holding material from the top part of the chamber tothe bottom part of the chamber at a location away from the outlet suchthat an area at the bottom part of the chamber is vented through thehole but the outlet is not vented through the hole.
 9. A cartridge,comprising: a chamber for holding a fluid; an outlet from the fluidholding chamber; a plurality of pieces of foam in the chamber, eachpiece of foam contacting another of the pieces of foam and one of thepieces of foam covering the outlet; a free fluid area defined by an areawithin the chamber not occupied by foam; and a hole in a piece of foamnot covering the outlet, the hole extending through the piece of foam tothe free fluid area.
 10. The cartridge of claim 9, wherein the fluidcomprises ink.
 11. The cartridge of claim 9, wherein the hole extendsthrough the piece of foam from a vented area of the chamber to the freefluid area at an otherwise substantially unvented area of the chambersuch that the free fluid area is vented through the hole.
 12. Thecartridge of claim 9, wherein: the free fluid area comprises a pluralityof discrete free fluid areas each defined by an area within the chambernot occupied by foam; and the hole comprises a plurality of holes eachextending through the piece of foam to one of the free fluid areas. 13.The cartridge of claim 12, wherein there are fewer holes than free fluidareas such that there is not a hole extending through the piece of foamto at least one of the free fluid areas.
 14. An ink cartridge,comprising: a housing defining a chamber for holding ink, the chamberhaving a first part occupied by foam and a second part not occupied byfoam and the housing having an opening therein to the atmosphere at thefirst part of the chamber; the foam having a hole extending therethrough from the first part to the second part such that the second partof the chamber is exposed to the atmosphere through the hole and theopening in the housing at the first part of the chamber.
 15. The inkcartridge of claim 14, wherein the second part of the chamber ispartitioned into a plurality of areas not occupied by foam and the holecomprises one or more holes each extending through the foam to one ofthe partitioned areas.
 16. The ink cartridge of claim 15, wherein thereare fewer holes than partitioned areas such that at least one of thepartitioned areas is not exposed to the atmosphere through a hole. 17.The ink cartridge of claim 14, further comprising: an outlet from theink holding chamber; and foam covering the outlet.
 18. The ink cartridgeof claim 17, further comprising a printhead operatively connected to thechamber through the outlet.
 19. A method, comprising: inserting a foamink holding material into an ink chamber in a body of an ink cartridge;and then forming, with heat, a hole through the foam from a top of thematerial to a bottom of the material.
 20. The method of claim 19,further comprising installing a lid on the body covering the ink chamberand then adding ink to the foam in the ink chamber.
 21. The method ofclaim 19, wherein forming the hole with heat comprises inserting aheated rod into the foam.
 22. The method of claim 21, wherein insertinga heated rod into the foam comprises inserting a rod having atemperature in the range of 225° C. to 400° C. into the foam.
 23. Themethod of claim 19, wherein forming the hole with heat comprises forminga plurality of holes serially by inserting a single heated rodrepeatedly into the foam.
 24. The method of claim 19, wherein formingthe hole with heat comprises forming a plurality of holes simultaneouslyby inserting an array of heated rods into the foam.
 25. The method ofclaim 19, wherein forming the hole with heat comprises applying pressureand heat to the foam simultaneously.